Intracorporal medical devices have been developed and used to navigate and access the tortuous vascular and other hollow conduits of a mammalian body. Some of these devices include guidewires, catheters, intravenous guidewires, stylets, intravenous catheters and related devices like endoscopes and colonoscopes that have a predetermined degree of flexibility and may have straight or pre-formed, shaped ends to guide the device through the anatomical conduit. Of the devices that are employed to reach vascular blockages, each has certain advantages and disadvantages. Many fall short of desired performance before reaching a vascular blockage because of a device prolapse at a vascular bifurcation, an inability to enter a bifurcation or be directed to the site of therapy. Others may reach an occlusion but then require a different device to be introduced before crossing the stenosis. The medical industry has striven to reach a balance between the flexibility required to negotiate around tortuous pathways and the rigidity necessary to stabilize a catheter's advancement. Many products such as intravenous interventional guidewires provide directability, flexibility or stiffness but fail to do all or a combination at the same time. These products typically have pre-formed flexible distal ends that provide minimal directability but not true directability, flexibility and stiffness combined, which would be the most useful advantage. Additionally, most physicians must use a series of different diameter guidewires to perform one procedure, creating a procedure that costs additional time, money and risks patient safety from vascular injury.
Accessing occlusions having relatively sharp angles and passage constrictions using conventional guidewires having pre-formed “J” shapes or angled distal ends requires rotating the guidewire while simultaneously moving it proximally and distally. This action can cause damage to the fragile endothelial cell layer lining blood vessels. Additionally, conventional guidewires can lose their ability to be rotated when the flexible distal ends enter vessels of reduced diameter. Rotation of the guidewire following inserting the distal end into a vessel having a reduced diameter produces high frictional forces between the walls of the small vessels and the guidewire. A desirable device would therefore require reduced rotation and increased ability to advance in a forward or distal direction through tortuous anatomies.
Another undesirable characteristic of conventional guidewires is the inability to support a catheter at the flexible, tapered, distal end. When a catheter is advanced toward a vascular location in and close to a bifurcation, the catheter tends to proceed in a straight line rather than following the guidewire, defined as prolapse. Further, the natural pulsation of the vascular system of a living animal can cause a conventional guidewire to move into or out of the body during the procedure, thereby losing its distal location.
An additional disadvantage of a general use catheter is that it must be inserted into the body over a guidewire. Therefore, both a catheter and a guidewire must be used to reach a targeted site within the body. A single device that functions as an independent guidewire or both a catheter and a guidewire would save procedural time, reduce patient recovery time and cause less vascular damage to the patient.
Still another disadvantage related to current practices resides in the catheter itself. Conventional catheters typically have totally open distal ends. Manufacturers have made efforts to design catheters with soft distal ends to minimize the extent of vascular damage when the open end engages the interior wall of blood vessels. This scraping of the endothelial layer results in a triggering of the auto immune system, causing clots to form at the damage site. Also, the distal end of the catheter may become clogged with material removed from the interior wall of the blood vessels. It is apparent that this bolus of material will be expelled from the distal catheter end when another device is inserted through the catheter. An all-in-one device having a soft, closed distal end that opens to allow other devices to be deployed from the distal end and then re-closing when the devices are withdrawn, would resolve this problem.
Once the occlusion is reached, the objective is to cross the blockage with the guidewire or remove the guidewire and insert yet another device to cut through the occlusion. This is inherently disadvantageous in that additional time is required and a greater risk of vascular damage or perforation of the vessel wall is presented. Conventional devices used to cross the blockage are generally stiffer than conventional guidewires and when inside the catheter and reaching a bifurcation can cause the more flexible catheter to move away from the target site and follow the guide into the opposite branch of the bifurcation.
Physicians generally have four objectives when using such vascular devices: (1) To reach the occlusion; (2) To reach the occlusion without causing vascular damage; (3) To cross the occlusion once it is reached; and (4) To reach the occlusion and cross it in as little time as possible. A device able to accomplish all four objectives would be extremely advantageous. It is not uncommon for a physician to place a catheter somewhere in a vessel and exchange the first guidewire with one or more secondary guidewires having progressively stiffer distal ends to prevent prolapse of the devices placed over the guidewire(s). Yet another advantage would be having a guidewire stiff enough to be pushed and yet be directed into branched vessels with minimal torquing. Still another advantage would be a multi-function device able to carry a second device that could bore its way through an occlusion.
Vascular occlusions defined as Chronic Total Occulsions are blockages that can occur anywhere in a patient's vascular system, including coronary, carotid, renal, iliac, femoral, cerebral, popliteal and other peripheral arteries.
U.S. Pat. No. 4,676,249 to Arenas discloses a guidewire having a moving internal member to provide stiffness when required, but does not disclose a directable distal end or the ability to cross occlusions. Another U.S. Pat. No. 5,542,434, discloses a longitudinally movable core wire made of a memory metal alloy that stiffens when subjected to thermal energy. This allows the wire to become stiff and yet torquable when desired, but fails when a catheter needs to be slid over the device. Both devices are deficient when they reach an occlusion with heavily calcified plaque in that they do not have the ability to bore through the occlusion.
Using a conventional guidewire to reach the occlusion requires a catheter to be pushed over the guidewire, the final guidewire removed and then another device to be pushed through the catheter and used to cross the blockage. Such devices are generally known as percutaneous transluminal thrombectomy or artherectomy devices. These devices have various means to cross the occlusion and are singular devices lacking the ability to solely navigate the vasculature. As an example, one such device is disclosed in U.S. Pat. No. 6,945,951 and describes a thrombectomy catheter using high velocity saline through jets that erode away the blockage and cross an occlusion.
For all these and other reasons there is a clear need for a single device that can vary its distal end, is relatively stiff, has the ability to cross an occlusion and/or a feature that can drill or bore its way through an occlusion.